Geosynthetics June/July 2023 - 30

Embankment reinforcement using 1750 kN/m strength geogrids
of the embankments. In addition, woven
polypropylene geotextiles were needed to
provide separation and reinforcement for
working platforms.
For the stabilization of the embankments
on this area, geogrids of different
strengths were specified, with tensile
strengths ranging from 350 kN/m (24,000
lb/ft) to 1,750 kN/m (120,000 lb/ft).
FIGURE 2 Extents of the Florianopolis Ring Road (Arteris Litoral Sul/Contorno Viário/divulgação)
began in 2020, is currently ongoing and is
expected to be completed in 2023.
The project is divided into several
sections, and the pedological conditions
of each section imposed different
needs on the project. The most critical
section in which the high-strength
geogrids were used was the south section,
located in the municipality of
Palhoças in Santa Catarina.
The 15-km (9-mile) long segment
FIGURE 3 Standard Penetration Test (SPT) on
the Florianopolis Ring Road area, South Section.
(Huesker Ltda., 2021)
goes over rugged terrains and therefore
required the construction of several tunnels
as well as embankment with heights
ranging up to 12 m (39 feet) in other
areas to achieve the design-required
alignment for the variant. The geology
in this section can be characterized in
two domains: the crystalline domain,
which consists of predominantly igneous
and metamorphic rocks of the crystalline
basement, and the sedimentary domain,
where sediment deposition occurs mainly
by marine fluvial processes. This second
domain goes from km 226+900 on
alignment to the BR-101 intersection.
The high-strength geogrids were used on
several segments and bridge abutments
due to the presence of thick layers of soft
soils to ensure the geotechnical stability
30
Geosynthetics | June July 2023
Reinforcement tensile
strength for embankments
on soft soils
The soft soil present in this area is characterized
by deep layers and low bearing
capacity, and one of the solutions adopted
was the use of geogrids to reinforce the
embankments, where the geosynthetic
acts as a passive reinforcement.
The foundation soils, when moving
horizontally under the weight of the
embankment, induce deformations in
the geosynthetic, mobilizing a resistant
traction force, restricting the displacement
of the soil layers, and bringing the
set to equilibrium.
The design strength of geosynthetic
reinforcement should be based on the
strength available at the end of the design
life (TCR), also known as the long-term
design strength (LTDS), especially when
geosynthetic reinforcements are subject
to creep strain. This strength may be
determined from isochronous load/strain
(creep) curves; see, for example, Figure 4.
The design tensile strength of the geosynthetic
reinforcement for ultimate limit
state (ULS) TD(ULS) is given by:
Where:
TCR: tensile creep rupture strength for
the appropriate design life and temperature
of the reinforcement
Geosynthetics June/July 2023

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